Enumerating and analyzing circulating tumor cells (CTCs)—cells that have been shed from primary solid tumors—can potentially be used to determine patient prognosis and track the progression of disease. There is a great challenge to create an effective platform that can isolate these cells, as they are extremely rare: only 1-10 CTCs are present in a 7.5mL of a cancer patient’s peripheral blood. We have developed a novel microfluidic system that can isolate CTC populations label free. Our system consists of a multistage separator that employs inertial migration to sort cells based on size. We demonstrate the feasibility of our device by sorting colloids that are comparable in size to red blood cells (RBCs) and CTCs.
Current technologies for cell surface marker screening such as flow cytometry and florescence microscopy, though indispensable, are not well suited for deployment in low resource or point-ofcare settings. Recently, node-pore sensing (NPS) has emerged as a microfluidic platform for labelfree cell surface marker screening. In NPS the transit time of individual cells being flowed through an antibody-functionalized microchannel are measured. Cells that express surface markers corresponding to a functionalized region are delayed due to specific, transient interactions with the surface. In this manner, the presence or absence of a particular surface marker is determined with single cell resolution. Here we show that by measuring the transit time optically as opposed to electrically, the abilities of NPS can be extended. We demonstrate this approach through measurements on human breast cancer cells. The technology presented here could potentially be deployed in low-resource settings as a diagnostic tool.
We will discuss two recent directions of our work: (1) The influence of submicron length scales on polymer dynamics, (2) Ultra-rapid mixing via sub-micron hydrodynamic focusing. (1) Polymer dynamics at sub-micron length scales. We have explored the changes in the dynamics of long polymers as the thickness of the quasi-2 dimensional space is varied from 0.09 microns to 10 microns. We will show how the thickness of this space, scaled with the persistence length of the polymer, changes the dynamics of the polymer. The consequences of this qualitative change in polymer dynamics is quite important, since it controls the elongation of the polymer at a given force field and hence the ability of he array to fractionate the polymer. (2) Mixing at the sub- micron length scale cannot be tubulent but only diffusive in nature. We will show how it is possible using hydrodynamics to produce liquid jets of width under 20 nanometers which can mix fluids in under 1 microsecond times.